In the conventional art, the technology of electric drills is getting gradually mature. As shown in FIG. 4A and FIG. 4B, the electric drill of conventional art commonly comprises a handle 1, a body 2 and a drill chuck 3. The handle 1 is provided with a battery 4 at one end of it, and provided with a switch 5 inside of it. The body 2 is provided inside with a motor 6 and an impeller 7 fixed to the rotational axle or shaft of the motor 6. The impeller 7 rotates with the motor 6 to produce an air current to cool the motor 6. The air current enters the body 2 through air inlets 8 and discharges through air outlets 9.
However, during the continuous use of the electric drill, the battery 4 and switch 5 of the electric drill will both produce heat. With longer continuous use, more heat is produced. If the cumulated heat is not dissipated in time, the service life of the battery 4 and switch 5 will be seriously influenced.